Americans Mario Capecchi and Oliver Smithies and Briton Martin Evans were awarded the prize for developing a technology known as gene targeting. The widely used process has helped scientists use mice to study heart disease, diabetes, cancer, cystic fibrosis and other diseases.

Capecchi, 70, who was born in Italy, is at the University of Utah in Salt Lake City. Smithies, 82, born in Britain, is at the University of North Carolina in Chapel Hill. Evans is at Cardiff University in England.

Capecchi says he was in a deep sleep when he got a phone call from the Nobel committee. He says the voice on the other end of the line sounded “very serious,” so his first reaction was that it had to be real.

Smithies says it’s nice to be recognized after working on the research for more than 20 years. He says he hopes winning the prize will make it easier to get funding for other work.

The first mice with genes manipulated in this way were announced in 1989. More than 10,000 different genes in mice have been studied in this way, the Nobel committee said. That’s about half the genes the rodents have.

“Gene targeting has pervaded all fields of biomedicine. Its impact on the understanding of gene function and its benefits to mankind will continue to increase over many years to come,” the award citation said.

Capecchi’s work has uncovered the roles of genes involved in organ development in mammals, the committee said. Evans has developed strains of gene-altered mice to study cystic fibrosis, and Smithies has created strains to study such conditions as high blood pressure and heart disease.

The medicine prize was the first of the six prestigious awards to be announced this year. The others are chemistry, physics, literature, peace and economics.

The prizes are handed out every year on Dec. 10, the anniversary of award founder Alfred Nobel’s death in 1896.

Last year, the Nobel Prize in medicine went to Americans Andrew Z. Fire and Craig C. Mello for discovering RNA interference, a process that can silence specific genes.